Generally, an oil-filled transformer is provided with a transformer main body and a tank configured to house the transformer main body. The transformer main body includes a high-voltage coil, a low-voltage coil and an iron core. The tank is filled with insulating oil, and the transformer main body is immersed in the insulating oil.
The tank is generally made of steel material. In order to prevent a magnetic flux leaked out of the transformer main body from entering into the tank, an electromagnetic shield is mounted on an inner wall of the tank.
For example, Japanese Patent Laying-Open No. 60-219717 (PTD 1) discloses an electromagnetic shield used in a transformer. The electromagnetic shield is formed to include a plurality of stacked magnetic thin plates and a pair of metal plates sandwiching the plurality of magnetic thin plates. A plurality of seat plates are prepared for mounting the electromagnetic shield in the tank. The plurality of seat plates are joined to the electromagnetic shield and to the inner wall of the tank by welding. Thereby, the electromagnetic shield is mounted in the tank.